1. Field of the Invention
The present invention relates to an optical beam expander with a function of laser power detection, and more particularly to an optical beam expander for increasing the stability of the laser ray power generated from a self-controlling power circuit without increasing the size of the optical beam expander.
2. Description of the Prior Art
In general, the laser diode is used to receive light leakage generated from a rear face of thereof by using a photodiode and feeding back the light current to the self-controlling power circuit so as to control the stability of the output light. However, an unstable laser ray power sometimes occurs due to the variable proportion of the backward output light and the forward output light. A large laser places a beam splitter and photodiodes at the front of the light-passing opening to transform a portion of the laser ray power into light current so as to control the laser ray power. A large laser is able to provide a more stable laser ray power; however, it has a large volume because of the extra devices added.
A diode-pump solid-state green laser usually contains an optical beam expander because it has a smaller diameter and a large divergence angle for expanding the laser beam and reducing the degrees of the divergence angle. Because the laser backward light is extremely weak and contains infrared components, it is not possible to control the laser ray power like the laser diode.